Fuse substance and art of producing same



Patented May 17, 1938 UNITED STATES PATENT OFFICE 2,117,282 FUSESUBSTANCE AND ART or monoc- ING AME

Frederick D. Austin, Port Chester, N. Y.

No Drawing. Application September 17,

Serial No. 40,999 3 Claims. (01. 200-142) ness is desired from the factthat the eutectic point of alloys in many instances is not thetemperature desired as that for effecting the fusing action. It has,accordingly, been proposed to vary the fusing point by varying theproportions of the constituents of the alloy to give the desired fusingpoint. This, however, has been found to result frequently in anundesirable action on the part of the fusing material from the fact thatit loses its stability and its tensile and compression strength andbecomes somewhat plastic before it actually reaches the fusing state.With electrical apparatus, and particularly such as is placed undertension for breaking a circuit when the fuse element is fused, thetension is likely to and under some circumstances does cause movement ofthe contact parts in the direction for breaking thecontact when thefusing material becomes plastic and before fusing occurs. This givesrise to such defects as arcing and variation from the desired point ofrelease temperature, and under some circumstances may, by sufficientelongation of the fuse material while plastic, cause complete failure tobreak the circult as intended. It is, therefore, highly desirable toprovide a fusing material possessing tensile and compression strength,which will be hereinafter referred to as stability, up to the exacttemperature of complete fusing, so that the fuse is solid and strong onemoment and the next moment is liquid, whereby a sharp break in thecircuit or a sharp response to any mechanical apparatus controlled by afuse is afforded without any intermediate period of elongation or otherdistortion of the fusing material due to plasticity.

An object of the present invention is the effective avoidance of anydeleterious or substantial or prohibitive period of plasticity precedingfusing on the part of fusing material, whereby stability of thefusingmaterial is preserved substantially to the moment of complete fusing.

A eutectic mixture or alloy is a mixture or alloy havingsuch proportionsof its constituent elements that it melts at the lowest temperature atwhich any alloy or mixture of the same constituents will melt, and theeutectic point is the fusing point of the eutectic mixture. A eutecticalloy possesses stability substantially to the moment of fusing, andtherefore, has substantially no period of plasticity in approachingfusing. But if it is desired to vary the fusing point from that of the 5eutectic and a different proportion of the alloyed metals is employedfor that purpose, then in most instances the stability is not preservedand a period of plasticity preceding fusing becomes substantial andpronounced. 10

It is an object of the present invention to provide a range of differentfusing points by alloys modified from a eutectic mixture with nodeleterious loss of stability, even though a partial plasticity of oneor more of the lower melting- 15 point constituents necessarily occursat a temperature below the desired breaking or fusing point. Althoughabsolute stability and absolute freedom from plasticity preceding fusingis not possible, it is so nearly approached by the pres- 2o entinvention as to avoid any objectionable plastic period preceding fusingwhile complete fusing is assured at the desired temperature within avery limited range of variation not exceeding three degrees (3) above orthree degrees (3) 25 below the intended point of breaking or completefusing.

While the addition of a modifying element to a eutectic mixture, as athird element to a binary eutectic alloy, will result in a mixture oralloy that does not have the sharp fusing point of the original eutecticin the sense that it will not change abruptly at a given temperaturefrom a completely solid state to a completely liquid state,

yet the present invention provides for such addi- 35 tion without adeleterious departure from such abrupt change or sharp fusing. To thisend, the third or added element is, according to the present invention,kept within the limits assuring effective action of the fuse under anexternal sep- 40 arating stress. That is to say, the complete alloy, asmodified by addition to the eutectifeross proportions, is such that itwill, upon approach ing the fusing temperature, be partly in a liquidand partly in a solid state, but the tensile strengtlr of the solidportion will be sufficient to prevent any plasticity or mushy" period orcondition of the mass as an entirety enabling it to elongate or stretchunder external stress, so that when the element or component of thealloy that melts at the lowest temperature becomes liquid within themass the remaining solid portions of the mass prevent softening of themass as an entirety, and

afford the desired stability of the mass until the predetermined highertemperature is reached where the whole mass becomes substantiallyabruptly liquid.

Hence, even though the alloy resulting from the present invention maynot always have an actual sharp fusing point, as is true of a eutecticmixture or alloy, yet the proportions of the elements of the massaccording to the present invention must always be such and of suchmaterials relative toeach other that the melting of the more readilymelted component or element will not deleteriously affect the sharpfusing of the whole mass. It is accordingly an important object of thepresent invention that, whatever may be the alloy,- the fuse substancecomprising such alloy will possess the two important qualities of(first) complete fusing at an established temperature with absolutedependability and without ob- Jectionable variation therefrom, say notexceeding a variation of more than three degrees above or three degreesbelow the established temperature, so that the point of complete fusingis critical, and (second) the fuse substance, retains sufflcient tensilestrength, even after its lowestmelting-point-element or component hasbecome liquid to resist the external separating stress to which the fusesubstance is subjected, and thus to insure abrupt separation of the fusesubstance when it reaches the predetermined desired temperature, so thatthe limits indicated for the relative proportions of the substancesemployed are critical.

An illustrative instance of effective use of embodiments of the presentinvention is found in the circuit control apparatus of my co-pendingapplication, Serial Ito/630.742, filed August 27, 1932, of which thisapplication is a continuation in part. This application is a substitutefor and a continuation in part of my co-pending application Serial No.723,997, filed May 4, 1934, which was a substitution for andcontinuation in part of my then co-pending application Serial No.666,931, filed April 19, 1933. The last-named application contains aclerical error in omitting to mention that, of the initial or primaryalloys A and B referred to therein, only forty (40) parts of suchinitial or primary alloy is taken in any one instance for the namedproportions of the added material, so that through the clerical error anerroneous proportion of parts is indicated, as will readily becomeapparent to one preparing and testing the alloys referred to in saidapplication Serial No. 666,931.

The substitution of the instant application for my co-pendingapplication Serial No. 723,997, filed May 4, 1934, is made because offailure in that application to specifically set forth the common basisor genus from which the several species spring, and also because, whilesaid last-named co-pending application recites the same proportions ofthe same elements for the same fusing temperatures, and thoseproportions and temperatures are critical, their critical character isnot specifically stated but is left in the said lastnamed co-pendingapplication to be spelled out from the whole disclosure or discoveredfrom tests. However, as a result of prolonged and carefully andscientifically conducted experimentation made by me in collaborationwith two eminent metallurgists, I am now able to state positively thatthe proportions and temperatures hereinafter set forth are in factcritical, and any appreciable or substantial departure from thehereinafter named limits of proportions of elements or componentsemployed will result in failure. The failure may either arise fromincapacity of the alloy ormixture to fuse at the desired temperature orwithin reasonably allowable variations therefrom (as three degrees aboveor three degrees below the named temperature) or from incapacity of themixture or alloy to preserve the necessary stability on approachingfusing temperature with a resultant incapacity for sharp separation onfusing; or the failure may involve both incapacity to fuse at thepredetermined temperature and incapacity to preserve stability up to thefusing point.

A further object of the present invention is to produce a fusing solderfor such devices as the circuit control apparatus of my'flrst-above-mentioned co-pending application, so that the parts may besoldered together and the solder utilized as the controlling fusingelement.

In carrying out the invention, I preferably produce-a trinary alloy,but, as will become apparent, the application of the invention isvaluable wherever available without regard to the number of metals ormetallic elements comprising the alloy.

While, of course, the alloy may be produced from a mixture in the firstinstance of the metallic elements hereinafter mentioned to produce thecompleted, finished alloy product, it has been found advantageous tofirst produce an initial or primary alloy and then modify its fusingpoint by the introduction of an additional metallic element in suchrelative proportion as to provide the required fusing point withoutdeleterious departure from abrupt fusing, so that the stability ispreserved and the plastic period preceding fusing largely eliminated.

As illustrative of the invention, three initial or primary eutecticalloys identified as A, B, and C are as follows:

(A) Bismuth and lead, having fifty-eight (58) parts bismuth to forty-two(42) parts lead by weight, and fusing at 257 F.; that is to say, analloy of fifty-eight (58) per centum bismuth and forty-two (42) percentum lead by weight is eutectiferous and fuses sharply at 257 F.

(B) Tin and lead, having sixty-three (63)- parts tin to thirty-seven(3'7) parts lead by weight, and fusing at 358 F'.; that is to say, an

alloy of sixty-three (63) per centum tin and thirty-seven (37) percentum lead by weight is eutectiferous and fuses sharply at358 F.

(C) Tin and copper, having ninety-nine (99) parts tin to one 1) .partcopper by weight, and fusing at 440.6" E; that is to say, an alloy ofninety-nine (99) per centum tin to one (1) per centum copper by weightis eutectiferous and fuses sharply at 440.6 F.

To vary the fusing point of these alloys, while preserving substantiallytheir stability and freedom from a deleterious plastic period precedingfusing, to the Alloy A should be added certain proportions of tinhereinafter recited to give the respective fusing points hereinafterrecited; and to the Alloys B and C should be added certain proportionsof bismuth hereinafter recited to give the respective fusing pointshereinafter recited.

As a matter of convenience in preparation, I have employed theproportions of added metallic elements with respect to forty (40) partsonly of the amount named of the initial or primary alloy (A, B, and Crespectively), and the following lists so indicate.

Eleven (11) alloys having eleven (11) different fusing points, ashereinafter indicated, may be produced from the initial or primaryAlloys A, B, and C by addingthereto the tin, or the bismuth, as the casemay be, respectively in the proportions recited in the following lists:

To forty (40) parts of Alloy A add five and two-tenths (5.2) parts tinto fuse at 212 F. Thus the proportions of the elements in the finalalloy are 51 %1s% or approximately 51%% bismuth to 37 %1s% orapproximately 37%% lead, and 11 "/11a% or approximately il tin to fuseat 212 F.

To forty (40) parts of Alloy A add three and twenty-five hundredths(3.25) parts tin to fuse at 222 F. Thus the proportions of the elementsin the final alloy are 53 A-ra% or approximately 53%% bismuth to 38 %m%-or approximately 38%% lead, and 7 %7 or approximately 7 tin to fuse at222 F. 1

To forty (40) parts of Alloy A add one and two-tenths (1.2) parts tin tofuse at 240 F. Thus the proportions of the elements in the final alloyare 56 %03% or approximately 56%% bismuth to 4 %ba% or approximately40%% lead, and 2 55037 orapproximately 2%,% tin to fuse at 240 F.

Toforty (40) parts of Alloy A add eight-tenths (.8) parts tin to fuse at245 F. Thus the proportions of the elements in the final alloy are %1%or approximately 56% bismuth to %1% or approximately 41%% lead, and 1'or approximately 1%% tin to fuse at 245 F.

To forty (40) parts of Alloy B add nine and two-tenths (9.2) partsbismuth to fuse at 265 F. Thus the proportions of the elements in thefinal alloy are 51%1% or approximately 51%% tin to %2a% or approximately30% lead, and 18 9i2s% or approximately 18%% bismuth to fuse at 265 F.

To forty (40) parts of Alloy B add five (5.0) parts bismuth to fuse at298 F. Thus the proportions of the elements in the final alloy are 56%tin to 32%% lead, and 11%% bismuth to fuse at 298 .F.

To forty (40) parts of Alloy B add three and two-tenths (3.2) partsbismuth to fuse at 332 F. Thus the proportions of the elements'in thefinal alloy are 58%% tin to 34 ,5 9}, or approximately M lead, and 7 %1%or approximately 736% bismuth to fuse at 332 F.

To forty (40) parts of Alloy B add two (2.0) parts bismuth to fuse at338 F. Thus the proportions of the elements in the final alloy are 60%tin to 35 /6196 or approximately 35%% lead, and 4 %1% or approximately4%% bismuth to fuse at 338 F.

To forty parts of Alloy B add one and two-tenths (1.2) parts bismuth tofuse at 350 F. Thus the proportions of the elements in the final alloyare 61 %0a% or approximately 61%% tin to 35 /ioa% or approximately 35%o%lead, and 2 %os% or approximately 2% bismuth to fuse at 350 F.

To forty 40) parts of Alloy C add two (2.0) parts bismuth to fuse at 410F. Thus the proportions of the elements in the final alloy are 95 /io41%or approximately 95%o% tin to A .or approximately 34 copper, and 491041% or approximately bismuth to fuse at 410 F.

To forty (40) parts of Alloy C addone (1.0) part bismuth to fuse at 425F. Thus the proportions of the elements in the final alloy are %21% orapproximately 97%% em t 2% "deleterious departure from the orapproximately ,5 copper, and 2 %s4% or approximately 2 bismuth to fuseat 425 F.

Thus, a binary alloy is changed to a trlnary alloy to vary the effectivefusing point of the binary alloy without appreciably varying thestability or capacity of the fusing material to resist becomingdeleteriously plastic prior to complete fusing, and, in each instance,the trinary alloy is well adapted for such apparatus asset forth in myabove-mentioned patent application Serial No. 630,742.

While, for convenience, the procedure above outlined is preferredwherein a binary alloy is first prepared with which is alloyed a thirdmetallic element to modify the fusing point of the completed alloywithout occasionlng any deleterious variation from the stability of thecompleted or final alloy immediately preceding fusing, so that a plasticstate is largely avoided while atfording a dependable fusing point,namely a point in the temperature range at which the fuse changesabruptly froma rigid and strong,

state to its liquid easily-parting state, it will be obvious that theexact sequence in which the several elements "or components making upthe completed alloy are brought together is not controlling so longasthe proportions are maintained. Also, the making up of a bulk of binaryor initial alloy and the use of forty (40) parts thereof relative to thestated number of parts of the modifying metallic element or component tobe added is more or less arbitrary for convenience, and so long as theresulting proportions are maintained any actual quantities may be dealtwith. For example, instead of employing forty (40) parts of Alloy A withfive andtwo-tenths (5.2) parts tin, the Alloy A may be made up in thefirst instance of twenty-three and two-tenths (23.2) parts bismuth andsixteen and eighttenths (16.8) parts lead to which will be added fiveand two-tenths (5.2) parts tin to produce the final alloy. All of theparts are by weight. Or the Alloy A may be made up of fifty-eight (58)parts bismuth, forty-two (42) parts lead, and the whole bulk employedwith thirteen (13.0). parts tin. This can be carried, out throughout allthe alloys above indicated, and, of course, the ingredients for any onealloy may be alloyed in a single operation instead of two successivesteps so long as the proportions are preserved.

While the several specific, completed or trinary alloys described aboveare of particular value for temperature fuses and other fuses and otheruses, they are given as illustrative examples with respect to thebroader concepts of the invention which include other unnamed alloysdetermined by the temperature responsiveness required and the physicalfact of stability. Various other metallic elements, as is clear from theforegoing, may be alloyed in the manner above set forth to givedifierenttemperature ranges and fusing points, but in each instance the principleshould be followed of modifying the fusing point of a primary alloy bysupplemental substance without I eutectic fusing action. In this way,highly efiicient fuses are provided having any fusing point desired.

It will be apparent from the foregoing that the invention in addition tocomprehending an alloy product also comprises an art, mode or,

method under which certain steps are taken or executed to produce a newsubstance having high ly valuable and distinctive characteristics.

What is claimed is:- 1. A metallic fuse element consisting of an alloyof lead and the elements bismuth and'tin,

one of said elements being in eutectic proportion with comprising 15.that to a 2., alloy elements lead and the lead, and the other of saidelements il or less by weight of the alloy so the alloy will haverigidity under stress up predetermined temperature.

A metallic ruse element consisting of an of the elements lead, bismuthand tin, the

bismuth being in eutectic prom portion and the element tin comprisingiii or le as by weight of the alloy so that the alloy will have rigidityunder stress up to a predeter- FREDERICK D. AUSTIN.

